As a child, almost everyone has made Kool-Aid, or at least watched
their mother do it. Therefore, everyone knows that when you pour the sugar
and powder in the water, the water goes from clear water to red (for fruit
punch Kool-Aid). It also changes its flavor from water to that of sugary
Kool-Aid. Although everyone has witnessed this happen, and has enjoyed a
glass of Kool-Aid, not everyone has stopped to wonder why the water turns
red and tastes sugary.
The mixing of Kool-Aid depends on both diffusion of the Kool-Aid powder
through the water and the convective mass transfer caused by stirring the
contents of the glass. Remember that convective mass transfer is
basically diffusion made faster by stirring. Stirring the contents of the
glass moves the areas of lower concentration of Kool-Aid to the areas
where a lot of Kool-Aid powder exists.